Most souterrains are modest affairs, a single narrow passage or a couple of chambers used for storage or refuge. The one at Peake is something else entirely: a passage opening into at least fifteen, possibly seventeen, large chambers, each standing roughly one and a half metres high. And that is only what was accessible. A large stone blocked the way to still further chambers beyond.

The site came to light in 1755, when it was investigated by the Reverend Marmaduke Cox, whose account was recorded by the historian Charles Smith. What Cox found inside was remarkable and, depending on one's tolerance for eighteenth-century reportage, either extraordinary or extraordinary with a heavy pinch of salt. One chamber was said to contain five hundred skeletons. Another held five more, some of them burnt. Alongside the bones, investigators recovered a carved wooden comb and a comb-case, small personal objects of the kind that rarely survive but carry an immediate human weight when they do. Cox also noted that the souterrain lay about a hundred and fifty yards from what he called a Danish fort, a term commonly used at the time for ringforts, the circular earthwork enclosures built throughout Ireland in the early medieval period. That nearby ringfort almost certainly formed part of the same settlement complex, with the souterrain serving the community that lived and farmed within or around it. The combination of so many chambers, the volume of skeletal remains, and the blocked passage suggests a site that was used extensively, and perhaps at a moment of crisis, though the details of that story remain underground.